1. Field of the Invention
The present invention relates to a power supply boost control device and to a method for identifying and judging a fault location in a power supply boost control device.
Priority is claimed on Japanese Patent Application No. 2004-162071, filed May 31, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, there have been proposed automobiles and other vehicles comprising a power supply boost control device which generates a high voltage, as the power supply for, for example, active control engine mounts and injectors.
Such power supply boost control devices execute feedback control to maintain a boosted voltage, which is a boosting circuit output, at a predetermined value. In cases where the boosted voltage fluctuates despite the execution of feedback control, the power supply boost control device is judged to be faulty. Japanese Unexamined Patent Application, First Publication, No. 2000-125586 discloses the use of a CPU to monitor the terminal voltage of a boosting circuit in order to improve the accuracy of detection of faults in such power supply boost control devices.
Power supply boost control devices generally adopt a switching boosting circuit; a smoothing capacitor with comparatively large capacitance is used within the boosting circuit. Hence large rush currents may occur when the power supply of the boosting circuit is turned on. Hence in order to prevent fusion at contact points due to such rush currents, Japanese Unexamined Patent Application, First Publication, No. H11-308855 describes the provision of a precharge circuit, to charge the smoothing capacitor with charge prior to turning on the power supply, so as to reduce the magnitude of the rush current.
As explained above, faults are judged in a power supply boost control device based on the output voltage of the boosting circuit. However, a precharge circuit or similar is connected further upstream than the boosting circuit, so that even if a fault is judged to have occurred, it is difficult to judge whether the fault is in the boosting circuit itself, or in the precharge circuit or another circuit other than the boosting circuit, and so there is the problem that the fault location cannot be identified.
If the power supply boost control device is activated and run continuously without being able to identify the fault location, there is the problem that the load on the power supply boost control device is increased.
Moreover, if a voltage judgment unit are provided for the precharge circuit and other circuits other than the boosting circuit in order to identify the fault location within the power supply boost control device, there is the problem that the circuit configuration is made complex.